The aim of this research is to study the physiological role, and the immunotherapeutic potential, of the T cell-derived nonspecific immunoregulatory lymphokine, T-cell growth factor (TCGF) and of cloned tumor-specific T-cell populations in malignant disease in mice. In order to address these questions we will take advantage of several recent developments which allow the: (1) purification of large amounts of TCGF derived from homogenous cellular sources, i.e., T-cell hybridomas and lymphomas; (2) establishment of cloned lines of functional, antigen-specific T cells; and (3) construction of somatic cell hybrids secreting monoclonal antibodies specific for various antigens in general, and for several lymphokines in particular. This investigation will address the above questions by: (1) establishing cloned lines of helper and cytotoxic T lymphocytes specific for syngeneic tumor antigens and studying their cell-\and lymphokine-mediated interactions in vitro; (2) analyzing the in vivo immunotherapeutic effects of such T-cell lines, either alone or in combination with other modalities, i.e., chemotherapy and/ or purified TCGF preparations, in several syngeneic tumor systems; (3) constructing somatic cell hybridomas secreting monoclonal antibodies specific for TCGF and using such antibodies to develop quantitative assays for TCGF; and (4) evaluating the physiological role of TCGF by studying the effects of anti-TCGF antibodies administered in vivo on tumor-specific immune responses. It is hoped that information gained from these studies will help to elucidate the precise role of T-cell subsets in tumor-specific effector function in vivo and the physiological importance of TCGF, its association with, and immunotherapeutic potential in, various diseases and abnormalities of the immune system.